INFLUENCE OF PROCESSING ON THE SITE AND EXTENT OF DIGESTION OF HIGH MOISTURE BARLEY IN CATTLE

Two experiments were conducted to evaluate the effect of processing and method of ensiling on the digestion and utilization of high moisture barley (HMB) in cattle. In experiment 1, four Holstein heifers were assigned in a Latin square design to diets containing 70% barley, 25% alfalfa hay and 5% supplement on a dry matter (DM) basis. Diets differed only in the type of barley fed: rolled dry barley (R-DB), rolled HBM (R-HMB), ground HMB (G-HMB) or unprocessed HMB (U-HMB). In experiment 2, three Holstein steers were fed 85.2% barley, 10.2% whole plant barley silage and 4.6% supplement on a DM basis. Again, diets differed only in the type of barley fed: R-DB, rolled HMB from a pit silo (Pit-HMB) or rolled HMB from a Harvestore silo (HAV-HMB). In experiment 1, digestibility coefficients for animals fed R-HMB were significantly higher than observed for U-HMB. While not significant, a similar trend for decreased digestibility was observed for R-DB and G-HMB. Animals fed HMB had significantly lower ruminal propionate concentrations. In addition, the rate of degradation of the degradable DM and crude protein (CP) fractions was slower for HMB than for dry barley. In experiment 2, a trend to lower digestibility coefficients was observed for animal fed R-DB compared to those fed Pit-HMB or HAV-HMB. Ruminal propionate concentrations for animals fed R-DB also tended to be higher than for those fed the HMB diets. Dry matter and CP disappearances from nylon bags was substantially lower for Pit-HMB than for R-DB or HAV-HMB. The results suggest that replacement of dry barley by rolled or unprocessed HMB in the diet of animals fed high grain diets may contribute to a more stable rumen environment.